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Expression of P2X4 receptor by lesional activated microglia during formalin-induced inflammatory pain

Liang-Hao Guo1, Katrin Trautmann, Hermann J Schluesener

  • 1Institute of Brain Research, University of Tuebingen, Calwer Str.3, D-72076 Tuebingen, Germany. lianghao.guo@uni-tuebingen.de

Journal of Neuroimmunology
|May 12, 2005
PubMed

Insights

The P2X4 receptor (P2X4R), an ATP-gated ion channel, is expressed by microglia in the rat spinal cord during inflammatory pain. Its expression increases following formalin injection, peaking at day 7, and then subsides.

Area of Science:

  • Neuroscience
  • Immunology
  • Pain Research

Background:

  • The P2X4 receptor (P2X4R) is an ion channel activated by adenosine 5'-triphosphate.
  • Its role in inflammatory pain, particularly in the spinal cord, requires further elucidation.

Purpose of the Study:

  • To investigate the presence, distribution, and temporal expression of P2X4R in the rat spinal cord during an inflammatory pain model.
  • To determine if P2X4R is expressed by microglia in response to peripheral inflammation.

Main Methods:

  • Immunohistochemical analysis was performed on rat spinal cords at multiple time points (1, 5, 7, 14, 28 days) after formalin-induced hindpaw inflammation.
  • Expression of P2X4R, ED1, and EMAP-II was assessed to identify microglia and their activation state.

Main Results:

  • P2X4R was rarely observed in normal or saline-treated control rats.
  • Following formalin injection, P2X4R-positive microglia significantly increased in the spinal cord dorsal horn ipsilateral to the injury.
  • P2X4R expression peaked by day 7 and returned to baseline by day 14, correlating with increased activated microglia (ED1 and EMAP-II expression).

Conclusions:

  • This study provides the first evidence that P2X4R is expressed by microglia in the context of spinal inflammatory pain.
  • P2X4R plays a significant role in the neuroinflammatory processes underlying inflammatory pain in the spinal cord.

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